Let it go.......this whole thread isn't even worth it. just a ton of repost.

 

Well there's a lot of misinformation in here at the very least.

I feel like there's a common misconception that "engines detect lower octane fuel and go into limp mode" haha... that's NOT how it works.

Someone took like 10% of the actual factual information and just distorted the other 90% into myth.

The Bosch EFI system will compensate timing for knocking like all semi-modern engines but I believe there is a normal range for getting near the detonation limit for peak performance, and I think this argument is totally pointless (perhaps someone better at physics/math/engine design can correct me here) because I'm not sure an engine with ~9.35:1 compression ratio is capable of detonating with fresh 87 octane gas.

Maybe in extremely hot conditions with horrible old gas and a new fresh engine with high compression.. but that's pretty rare and in that case that's why we have the knock sensor.

The other thing we have to consider is that most of these old pushrod engines aren't going to even HAVE their original compression ratios, between valve seat wear and deposits etc.. no way, probably closer to 9:1.


As far as the poster about high altitude is concerned.. at the end of the day, it's either detonating or it's running perfectly fine (albeit lower power at higher altitude) there's nothing in between and nothing to "compensate" for.. BUT good gas is rather pointless at ~7000+ feet as the air is so thin that you're essentially getting less "energy" per stroke in fuel to maintain correct air/fuel ratio, detonating in this reduced performance scenario is basically impossible, at least in a non-forced-induction vehicle.

I've actually heard that they sell 85 octane gas in higher altitude climates, but yeah at the very least if many of us are running near 200k miles with 87 at sea level, you should be fine up there all day long!